Rotor construction for turbines



5 Sheets-Sheet 1 C. R. SODERBERG ROTOR CONSTRUCTION FOR TURBINES feb. s,1949.

Filed Aug. 23, 1944 Feb. 8, 1949. c. R. soDERBERG 2,46l,242

ROTOR CONSTRUCTION FOR TURIBINES Filed Aug. 23, 1944 3 Sheets-Sheet I5fm l F|G 3 O INVENTOR @fd/HM throughout.

Patented Feb. 8, 1949 UNITED s'rA'ri-:s PATENT 1 oFFlca 2,461,242 cflf"Z United Aircraft Corporation, East Hartford,v

Conn., a corporation of Delaware Applicants August 23, 1944, serial No.trasse This invention relates to gas turbines and the like andespecially to rotor constructions adapted for use in aircraft.

Turbines orcompressor-s generally have a heavy solid rotor having anumber of rows of blades alternating with rows of nozzles. in asurrounding casing. The casing is necessarily split lengthwise to permitassembly with the rotor. A feature of this invention is a rotor splitinto discs each carrying a row of blades to make possible assembly ofthe rotor with a casingl not having a longitudinal split.

Endwise assembly of an axial flow compressor or turbine having a solidrotor is difficult. if not impossible, although such endwise assembly isfrequently desirable. Another feature is a builtup rotor arranged topermit endwise assembly of the complete turbine. f A solid rotor isdiflicult to machine and dimcult to handle during assembly of the bladesand shrouds. Furthermore, it may be difllcult to obtain a solid piece ofmaterial from which the. rotor may be made which will be homogeneousSince the rotor may be highly stressed in operation, a flaw in the rotormay cause failure. An object of the invention is to avoid thesedilculties by a rotor built up of separate discs each having a row ofblades.

A feature of the invention is a built-up rotor held together by acentral bolt to form a unitary operative assembly. The bolt may betightened within the rotor by differential threads for a more rigidassembly.

Another feature is a light weight rotor which will make possible a lightweight turbine adapted for use in aircraft.

Other objects and advantages will be apparent from the specification andclaims, and from the accompanying drawings which illustrate anembodiment of the invention.

Fig. 1 is a sectional view through the turbine.

Fig. 2 is a fragmentary sectional view on a larger scale through thecentral bolt.

Fig. 3 is a fragmentary sectional view of the rotor.

The invention is shown in a turbine which in-4 cludes a casing i builtup of rings I2, It, i8 and i8 supported by radial pins 20 in a housing22.

These pins which are all in substantially the same plane and whichconstitute the support for the casing within the housing, engage boresin bosses 24 in one ring I4 of the casing. Rotor 28 within the casinghas a number of rows of blades 28 alternating with rows of nozzles 30 inthe casing.

Housing 22 has a head 24 which for'ms a part 4 Claims. (Cl. 253-39) ofthe housing 'and supports a bearing sleeve 22 for the front end of rotor28. At the other end of the turbine, the housing 22 supports a mountingl! within which is a bearing 40 for the rotor. Mounting. has a number oflegs 42 engaging with radial pins 44 which locate the mounting withinthe housing. Rotor 28 is made up of a number of thin. substantiallyflat. discs 48, 48, `Bil and 52. and shaftforming end elements or endbells 54 and 5B. The discs and the shaft elements are all held togetherby a central bolt 58. The ends of the'bolt are positioned within the endelements 54 and B6 and are connected to the end elements by threadedsleeves or nuts 80 and 82. Each sleeve 80, B2 has inner and outerthreads 84 and 88 engaging respectively with cooperating threads on thebolt and on the end elements. 0n one of the sleeves (sleeve as shown)the inner and outer threads may di'er in pitch so that as the sleeve isscrewed into place. a substantial tension may be applied to the bolt.

To avoid overstressing the center boit as the turbine discs `becomeheated and expand axially during turbine operation, theconnectionsbetween the center bolt and the surrounding shaft elementsare preferably adjacent the outer ends of the elements. The part of thebolt which must elongate to accommodate the axial disc expansion is thusrelatively long and will not be as highly stressed as a shorter boltwould be.

Since the casing is built up of casing rings bolted together, each ringhaving a row of nozzles. and since the rotor is built up of discs, eachhaving a row o f blades, it is apparent that the turbine is adapted forendwise assembly. To assist in aligning the discs during assembly and toprevent relative rotation in operation, each disc has projecting annularflanges 88 and 10 on opposite sides having interengaging elementspreferably in the form of face splines 12 cooperating with similarelements on the adjoining disc. Similarly, the inner ends of shaftelements 64 and 56 have face splines 'I3 cooperating with splines on theen d discs. The relatively thin flanges B8 and 10 are spaced fromcentral open.

ings 88, hereinafter described, at distances several times greater thanthe thickness of thel flanges and define, when the discs are assembled,a substantially rigid cylindrical support for, the discs. The flangesextend axially beyond the thickest part of the disc. Y

Gas enters the first stage nozzles of the turbine throughvan inletscroll 14 which' is attached to the end of casing I Il.' Leakage ofpower gas 3 i past the'outer ends oi the blades is prevented by seals 18which may be positioned between adjoining casing -ringsand leakage ofpower gas surrounding the inner edges of the diaphragm 18 extendinginwardly from each row of nozzles is on projecting radially from theperiphery and each having a central openingeach disc having asubstantially constant-stress cross-section,

' thereby being substantially thicker at the central prevented by alabyrinth seal 88. Gas from the bolt, and the shaft elements `54 and 58have centrai openings 88 and 88, Fig. 2, also larger in A diameter thanthe fastening bolt. The discs and shaft elements of the rotor are thusfree to expandv radially without affecting the alignment of the parts.Stability of the assembled rotor parts may be maintained by a number ofprojections 90 on the bolt engaging in radial grooves 82 in one of thedisc-s.

In applying tension to the bolt by the differential threads 84 and 86 onsleeve 80,. it will be apparent that, if thread 64 has a higher pitchthan outer threads 86, the sleeve will tend to move the bolt endwisewhile the sleeve is being screwed in. By selection of proper pitches, apredetermined tension may be applied to the bolt. For additionaltension, the bolt may be heated prior to assembly, so that, afterassembly, as the bolt cools, the contraction of the bolt will apply thedesired tension.

A It is to be understood that the invention is not limited to thespecific embodiments herein illusrtrated and described, but may be usedin other shafts together, the ends of the bolt being within the recessesin the shafts, said tie bolt having threads at each end, a nut `engagingthe threads at one end and engaging one of the shafts, another nutengaging the threads at the other end, one of said nuts having threadsof different pitch on inner and outer surfaces, one set of the threadson the nut engaging the bolt threads, the other threads on the nutengaging cooperating threads on the other projecting shaft.

2. A rotor construction including a number of discs each having a row ofblades, each disc having a central opening, a shaft at each end of theset of discs, and engaging the end disc, each shaft having a centralrecess, a tie bolt extending through the openings in said discs and intothe recesses in the shafts for holding the discs and shafts together,said bolts having threads at one "end, a nut having threads engagingsaid boit opening than over the remainder of the disc, the thicknessdecreasing rapidly toward the periphery of the disc, annular flanges onopposite sides of each disc extending axially of and concentric .4to thedisc, said flanges extending from the disc at a radius substantiallygreater than that of the central opening and at a radius where the discsare relatively thin, the spacing of the flange from the central openingbeing several times the thickness of the flange, the flanges of adjacentdiscs engaging with one another'and constituting the sole contactbetween the adjacent discs, each flange projecting axially beyond thethickest part of the disc, said flanges, when in engagement, defining asubstantially rigid cylindrical support for said discs with the diameterof the cylinder substantially greater than the diameter of the centralopening in the disc, a through bolt extending through said centralopenings and out of contact therewith for clamping said discs togetherwith the ends of the flanges in interengagement, and end beilsextendingbetween the ends of the through bolt and the ilanges on the outersurfaces of the endmost discs, said end bells having contact with thedisc only through said ilanges, said bolt holding said end bells againstthe end discs, and clamping the discs together.

4. A rotor including a number of thin substantially fiat discs eachhaving a row of blades thereon projecting radially from the periphery fand each having a'central opening, each disc having a substantiallyconstant-stress cross-section, thereby being substantially thicker atthe central opening than over the remainder of the disc, the thicknessdecreasing rapidly toward the periphery of the disc, annular flanges onopposite v sides of each disc extending axially of and concentric to thedisc, said flanges extending from the disc at a radius substantiallygreater than that of the central opening and at a radius where the discsare relatively thin, the spacing of the flange from the central openingbeing several times the thickness ofthe flange, the flanges of adjacentdiscs engaging with one another and constituting the sole` contactbetween adjacent discs. each flange projecting axially beyond thethickest part of the disc, said flanges, when in engagement, dening asubstantially rigid cylindrical support for saiddiscs with the diameterof the cylinder substantially greater than the diameter of the centralopening in the discs, a shaft at each end of the set of discs andengaging with the projecting flange at the outer side of each end disc,each shaft having a central recess, a tie bolt extending through theopenings in said'discs and into the recesses in the shafts for .holdingthe discs and shaft together,4 the openings in said discs being largerthan the bolt so that the discs are out of contact with the bolt. saidbolt having threads at one end, a nut having threads cooperating withthe threads on the bolt and fitting within the recess of and engagingthe adjoining shaft, and' means interconnecting the other end of, saidbolt and the other shaft for holding said other end of the bolt in fixedrelation to said other shaft such that the bolt holds the discs andshafts in assembled relation.

CARL a. soDEaBERG. (References on following page) Number REFERENCESCITED l 1,551,402 v The following references are of record in the2,213,940 111e of this patent: 2,308,233

UNITED STATES PATENTS 5 NumbelrY` Name vDate Number 788,830 HodgkinsonMay 2, 1905 282 806,720 Windhausen Dec. 5, 1905 541,584 923,724 SpradoJune 1, 1909 w 1,107,238 Kieser Aug. 11, 1914 Name Date -Junggren Aug.25, 1925 Jendrassik Sept. 3, 1940 lSchutte Jan. 12, 1943 FOREIGN PATENTSA Country Date Great Britain July 3, 1908 Great Britain Dec. 2, 1941Patent No. 2,461,242.

Certificate of Correction Y February s, 1949.

CARL R. SODERBERG It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows:

Column 3, line 65, claim 2, for the word bolts read bolt; and that thesaid Letters Patent should be read with this correction therein that they same may conform to the record of the case in the Patent Oce.

Signed and sealed this 21st day of June, A. D. 1949.

THOMAS F. MURPHY,

Assistant Uommasz'oner of Patents.

